Process of producing a rubber compound



Patented Feb. 23, 1926.

"UNITED STAT as PATENT. OFFICE.

HAROLD A. xon'ron, or AKRON, OHIO, Assronon TO THE MILLER RUBBERcompany,

OF A K RON, OHIO, A'CORP ORATION OF OHIO.

PiROCESSOF PRODUCING A RUBBER COMPOUND.

No Drawing.

To all whom it may concern Be it'known that I, HAROLD A. MoR'roN, acitizen of the United States, and resident of Akron, in the county-ofSummit and State of Ohio, have invented certain new and usefulImprovements in Processes of Producing a Rubber Compound, of which thefollowing is a specification.

My present invention relatesto an improvement in the art of vulcanizingrubber compounds and more especially to the use of vulcanizationaccelerators and the activators thereof. Y

Certain difficulties have always been encountered in the use ofingredients which accelerated vulcanization either by reducing theamount of time or temperature necessary for vulcanization. In the mixingand .calendering operations it was found that the presence of suchingredients causes partial or total vulcanization to occur prema-'turely due either to the heat generated from mixing the stock or used inwarming the calender rolls. It has been found that some accelerators areslower in action than others, so much so that where certain acceleratorswhen mixed in a rubber compound. will cause vulcanization to occur atordinary room temperatures in a few days time and at slightly highertemperatures in a few hours time. Others show an appreciable shorteningof the time of vulcanization only when raised to the temperaturesordinarily employed in vulcaniz'ing rubber compounds not containingaccelerators.

It has .been known for some time-that certain metallic oxides, which arethemselves not accelerators. enhance the action of mostorganic-accelerators. That is, the presence of a metallic oxideoftencauses the organic accelerator to act in a shorter time or at a lowertemperature. The cause of such action is not known but the effect isutilized universall in usual factory practice.

A. nota le-example of such a metallic oxide is zinc oxide which isprobably the most universally used compounding ingredient in the. rubberindustry.

Zinc oxide is not the only material which acts in this manner, some zincsalts and some other metallic salts act in this way. Such materials areusually termed activators. v I have discovered that rubber compounds maybe prepared containing unvulcanized Application filed April 8,

1924.. Serial No. 705,105.

that after such rubber compounds are calendered to produce a'thin sheetof rubber and thisflrubber is then dusted with finely powered zincoxideand the sheet then sub jected to vulcanization temperatures,vulcanization will occur at as low a temperature and in nearly as shorta-time as it would have occurred had the zinc oxide been thoroughlymixed into the original compound. However, it will readily be apparentthat if the zinc oxide had originally been mixed'in the compound, themixing and c'alendering of this stock would have been extremelydiflicult without burning or partially vu'lcanizing the stock. It willthus be seen that I have devised a new way by which the danger ofburnin'g or prevulcanization may be obviated. v

The action of the activator is diiiicult to understand but it wouldappear that the ac celerutor must have to migrate to the su'r- Parts.Smoked sheet rubber 97 A Dimethyl amine carbon bisulphide productSulphur 2 These ingredients'are thoroughly. incor-.

porated on a mixing mill and the compound is then sheeted outon acalender to a thickness of approximately 1/128 of an inch. As this sheetleaves the calender it is thoroughly dusted with finely divided zincoxide and is-then rolled up on itself and cured for a period ofapproximately 24 hours at Another method of operatingthis inventionconsists in mixin from the uncured and calendering the .stocl: intosheets bui ding the final article are 1,574,676

article in finely divided zinc oxide, either Having thus described myinvention, pure or diluted with an inert carrier (such What I claim is aas starch). The imbedded article is then The process of producingvulcanized rub- 1 heated to a temperature of 150 F. whereher whichconsists in mixing rubber with upon vulcanization takes place. sulphurand anaccelerator, calcndering the l'g; .is obvious that the rubbercompound same into a sheet of suitable thickness, apmay contain inaddition to sulphur and a plying an activator to the surface of the lowtemperature curing accelerator any of sheet, rolling the sheet uponitself, and cur- 20 the usua compounding ingredients which ingthe same.

159 are not activators. It is also obvious that In-testimony whereof,Iafiix my signature.

other activators may be used in place of zinc oxide. A. MORTON.

